SAS No. 144 amends AU-C 501 to require the auditor to perform which of the following with following steps with respect to a management's specialist: a. obtain an understanding of the work of the specialist b. negotiate the terms of the agreement to engage a management's specialist c. make recommendations to management about changes in scope that should be negotiated into the engagement letter with a management's specialist d. override management by deciding to engage an auditor's specialist in lieu of management hiring its own specialist